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A126716 Least i such that prime(i)*2^(10^n) -1 is prime. 0
2, 3, 51, 657, 6255 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
EXAMPLE
3*2^(10^0)-1=5 prime so a(0)=2 since 3 is prime(2).
3*2^(10^1)-1=3071=37*83 composite, 5*2^(10^1)-1=5119 prime so a(1)=3, since 5 is prime(3).
PROG
(PARI) a(n) = my(i=2); while (!isprime(prime(i)*2^(10^n) -1), i++); i; \\ Michel Marcus, Sep 15 2019
CROSSREFS
Sequence in context: A065646 A268251 A090508 * A355648 A347894 A362836
KEYWORD
nonn,more
AUTHOR
Pierre CAMI, Feb 13 2007
STATUS
approved

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Last modified July 13 08:08 EDT 2024. Contains 374274 sequences. (Running on oeis4.)